1. Field of the Invention
The present invention relates to a gas turbine engine with an intake air flow rate control mechanism for controlling the intake air flow rate according to operational conditions to burn gas.
2. Description of the Related Art
To suppress the discharge of an atmospheric pollutant such as NOx and CO from a gas turbine engine, there are various types of combustors. On the other hand, there is a strong demand from users of gas turbine generators for enlarging the operable load range thereof. However, when an operable load range of a generator is enlarged, the generator may be operated at an air-to-fuel ratio outside the proper range thereof suited to suppress a discharge of an atmospheric pollutant from a gas turbine engine, thereby the prescribed standard of exhaust gas may not be satisfied.
For example, for a gas turbine engine which is provided with a lean premixing combustor, there is a demand from users for extending the lean combustion operational range. To satisfy the demand, it is necessary to reduce the flow rate of air for combustion flowing into the combustor when the load is small. However, a gas turbine engine for a generator is generally operated at a fixed revolving speed, regardless of the magnitude of the load, thereby the air flow is determined without free choice. Thus, it is difficult to enlarge the operational range with satisfying the prescribed exhaust gas standard.
Further, in a gas turbine engine which is provided with a catalytic combustor, to enlarge the turn down ratio of catalytic combustion (same as the air-to-fuel ratio), that is, to reduce the air flow at the time of partial load, an air flow control mechanism for bypassing air so as to prevent a part of air from entering the catalytic combustor is installed in the catalytic combustor. However, the air flow control mechanism is complicated in its structure and expensive and moreover, the combustor is provided with a bypass flow path so that the structure inevitably increases in size.
Further, for the purpose of controlling the exhaust gas temperature of the engine, a gas turbine control unit provided with an inlet guide vane for adjusting the air flow is known (for example, refer to Japanese Patent Laid-Open Publication No. 57-68526).